/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "android-base/stringprintf.h"

namespace android {
    namespace base {

        void StringAppendV(std::string *dst, const char *format, va_list ap) {
            // First try with a small fixed size buffer
            char space[1024];

            // It's possible for methods that use a va_list to invalidate
            // the data in it upon use.  The fix is to make a copy
            // of the structure before using it and use that copy instead.
            va_list backup_ap;
            va_copy(backup_ap, ap);
            int result = vsnprintf(space, sizeof(space), format, backup_ap);
            va_end(backup_ap);

            if (result < static_cast<int>(sizeof(space))) {
                if (result >= 0) {
                    // Normal case -- everything fit.
                    dst->append(space, result);
                    return;
                }

                if (result < 0) {
                    // Just an error.
                    return;
                }
            }

            // Increase the buffer size to the size requested by vsnprintf,
            // plus one for the closing \0.
            int length = result + 1;
            char *buf = new char[length];

            // Restore the va_list before we use it again
            va_copy(backup_ap, ap);
            result = vsnprintf(buf, length, format, backup_ap);
            va_end(backup_ap);

            if (result >= 0 && result < length) {
                // It fit
                dst->append(buf, result);
            }
            delete[] buf;
        }

        std::string StringPrintf(const char *fmt, ...) {
            va_list ap;
            va_start(ap, fmt);
            std::string result;
            StringAppendV(&result, fmt, ap);
            va_end(ap);
            return result;
        }

        void StringAppendF(std::string *dst, const char *format, ...) {
            va_list ap;
            va_start(ap, format);
            StringAppendV(dst, format, ap);
            va_end(ap);
        }

    }  // namespace base
}  // namespace android
